1064. Complete Binary Search Tree (30)

    将节点键值排序，然后确定根节点，每次求根节点左边节点数目，这样递归下去，然后用BFS层遍历。

#include <iostream>#include <cstdio>#include <queue>#include <algorithm>using namespace std;int deep(int n){if(n <= 1) return 0;int h = 0;while(true){        if(n > (1<<h)-1 && n <= (1<<(h+1))-1) break;        ++h;}return h;}int leftSize(int n){    int h = deep(n);    if(h == 0) return 0;    int sum = (1<<h)-1;    if(n-sum <= (1<<(h-1))) return (sum-1)/2 + n-sum;    else return (sum-1)/2 + (1<<(h-1));}int main(){int n;cin >> n;vector<int> keys(n);for(int i = 0; i < n; ++i)        scanf("%d", &keys[i]);    sort(begin(keys), end(keys));queue<pair<int,int>> Q;Q.push({0, n});vector<int> result;while(!Q.empty()){        auto p = Q.front();        Q.pop();        int num = p.second-p.first;        if(num == 1) result.push_back(keys[p.first]);        else{            int left = leftSize(num);            int right = num-left-1;            result.push_back(keys[p.first+left]);            if(left) Q.push({p.first, p.first+left});            if(right) Q.push({p.first+left+1,p.second});        }}for(size_t i = 0; i < result.size(); ++i){        if(i) printf(" ");        printf("%d", result[i]);}return 0;}